Aquaculture Waste Goes Far too Far

US - Urine, fecal matter and uneaten feed from fish farms are being carried greater distances than previously thought, according to Stanford researchers.

Uneaten commercial feed gets carried off by currents, writes Catherine Ho for the Los Angeles Times. According to her, the fish -- often penned up by the thousands -- defecate and urinate, creating waste streams in the ocean.

It had previously been assumed that the waste matter would be diluted by the sea if farming pens were kept far enough from the shore, said Jeffrey Koseff, co-director of Stanford's Woods Institute for the Environment. But results from new software that simulates fluid dynamics show that waste from fish farming will travel farther and in higher concentrations than scientists thought, Koseff said.

The Los Angeles Times reports that the currents that flush out the pens could ultimately carry the waste to a public beach or mangrove ecosystem. But if not enough currents flow through the pen, fecal matter and uneaten food could pile up beneath the fish and create a "dead zone" on the ocean floor -- an area where there's not enough oxygen in the water for plants and animals to survive.